This invention relates to methods for growing waveguiding-type single crystals of rare earth pentaphosphates, particularly those of a nature suitable for optical device use.
The discovery of rare earth pentaphosphates particularly suitable for laser use has been previously disclosed in U.S. Pat. No. 3,813,613 of H. G. Danielmeyer et al., issued May 28, 1974. This type of laser material was found to have potential advantages over prior art types of rare earth-containing compounds, such as neodymium-doped yttrium aluminum garnet. The approximately 30 times higher concentration of neodymium leads to a relative miniaturization of devices and to a potential for reduced threshold for a side-pumped version of the laser.
It has been recently discovered that the prior art neodymium-containing crystals, such as yttrium aluminum garnet can be grown in a single crystal fiber form in which the pump light and the laser light are waveguided. Such a configuration is particularly advantageous in view of its compatibility with proposed optical fiber communication systems.
Clearly it would be advantageous to have rare earth pentaphosphate crystals in a similar waveguiding form, and perhaps with even smaller diameters and shorter lengths because of the higher concentration of the active ions. In addition, the number of axial and transverse modes permitted by the laser device should be clearly reduced in such a miniaturized device, as compared with the larger devices.